Background: Obesity is a major risk factor for mobility limitation in older adults. It is estimated that 11 million older adults have mobility disability and > 4 million older adults use walking assistive devices. Mobility disability results in decreased economy of gait, physical deconditioning and reduced peak aerobic capacity (VO2peak). Impaired economy of gait and decreased physiological reserve may lead to increased fatigue, reduced endurance, and ultimately contribute to reduced functional independence. The optimal intervention to improve mobility limitations in older, obese adults is not known, particular in those who use walking assistive devices, and there is limited information on whether improvements in physical function can be sustained over time. Preliminary studies demonstrate that our novel progressive group multimodal balance intervention (MMBI), focusing on lateral movements, lower extremity strengthening and dynamic obstacle negotiation can improve gait, balance, and strength in mobility limited older adults. However, it is no known if weight loss in combination with MMBI will provide additive or synergistic improvements in mobility limited older, obese Veterans. We hypothesize that our MMBI program in combination with a hypocaloric nutritional intervention (Nutrition) will be more effective than MMBI alone in improving muscle quality, physical function and economy of gait. In addition, we hypothesize that the Nutrition + MMBI will be more effective than MMBI alone at improving self- reported measures of function and disability. Objective: We propose a randomized clinical trial in 120 older (age > 60 yr) community-dwelling obese (BMI >30 kg/m2), Veterans with mobility limitations who use walking assistive devices in which we will: Specific aim 1: Compare the effects of a 6-month MMBI intervention alone to a 6-month combination Nutrition + MMBI on physical functioning and economy of gait. Specific aim 2: Compare the effects of the two interventions on body composition, muscle mass, strength and relative sarcopenia. Specific aim 3: Assess the effects of the two interventions at baseline, 6, 12 and 24 months on their self- reported measures of function and disability using the Late-Life Function and Disability Instrument (LLFDI). Methods: Veterans enrolled into the study will have baseline testing at the Baltimore GRECC and VAMHCS Human Performance Laboratory consisting of 1) performance-based outcome measures include VO2peak, gait speed (gait rite), chair stands, lateral mobility and balance (four square step test, figure eight), SPPB, handgrip strength (dynamometry), and economy of gait (portable VO2 measurement during 6 minute walk) and functional status (ADL, IADLs); 2) lower extremity strength testing, 3) total body DXA scan, and a CT scan of the abdomen, hips and thighs for determination of lower extremity and core muscle composition; and 4) biomarkers. After completion of baseline testing, the Veterans will be randomized to one of the two interventions. Nutrition classes will be led by a GRECC dietitian. The goal is for subjects to lose 10% of their weight over the first 6 months with gradual weight loss after that. The MMBI will consist of a group dynamic balance class, a supervised obstacle course, and lower extremity and core strengthening. After 3-, 6-, 12-, and 24-months, subjects will repeat the assessments that they had at baseline. Impact: Few exercise rehabilitation studies target older, obese Veterans who use walking assistive device and indeed individuals who use walking assistive devices are often excluded from the studies. This research directly benefits Veterans as it may lead to more effective interventions that improve mobility, reduce fall risk, and reduce injury-related hospitalization and death in older Veterans with mobility limitations. This nutritional and multimodal balance intervention is readily exportable to the community and with additional resources could be widely implemented at other VAs as part of clinical care.